Firefox

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;
import org.openqa.selenium.By;
import org.openqa.selenium.firefox.FirefoxProfile;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.JavascriptExecutor;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.util.Base64;
import java.net.URL;

public class script {

  public static final String USERNAME = "<username>";
  public static final String AUTOMATE_KEY = "<accesskey>";
  public static final String URL = "https://" + USERNAME + ":" + AUTOMATE_KEY + "@hub-cloud.browserstack.com/wd/hub";

  public static void main(String[] args) throws Exception {

    FirefoxProfile profile = new FirefoxProfile();
    profile.setPreference("browser.download.folderList", 1);
    profile.setPreference("browser.download.manager.showWhenStarting", false);
    profile.setPreference("browser.download.manager.focusWhenStarting", false);
    profile.setPreference("browser.download.useDownloadDir", true);
    profile.setPreference("browser.helperApps.alwaysAsk.force", false);
    profile.setPreference("browser.download.manager.alertOnEXEOpen", false);
    profile.setPreference("browser.download.manager.closeWhenDone", true);
    profile.setPreference("browser.download.manager.showAlertOnComplete", false);
    profile.setPreference("browser.download.manager.useWindow", false);
    // You will need to find the content-type of your app and set it here.
    profile.setPreference("browser.helperApps.neverAsk.saveToDisk", "application/octet-stream");

    DesiredCapabilities caps = new DesiredCapabilities();
    caps.setCapability("browser", "Firefox");
    caps.setCapability("browser_version", "latest");
    caps.setCapability("os", "Windows");
    caps.setCapability("os_version", "10");
    caps.setCapability("name", "Bstack-[Java] Sample file download");
    caps.setCapability(FirefoxDriver.PROFILE, profile);

    WebDriver driver = new RemoteWebDriver(new URL(URL), caps);
    JavascriptExecutor jse = (JavascriptExecutor) driver;

    // Navigate to the link
    driver.get("https://www.browserstack.com/test-on-the-right-mobile-devices");
    Thread.sleep(2000);

    // Accept the cookie popup
    WebElement pop = driver.findElement(By.id("accept-cookie-notification"));
    pop.click();

    // Find element by class name and store in variable "Element"  
    WebElement Element = driver.findElement(By.className("icon-csv"));

    // This will scroll the page till the element is found       
    jse.executeScript("arguments[0].scrollIntoView();", Element);
    jse.executeScript("window.scrollBy(0,-100)");
    Thread.sleep(1000);

    // Click on the element to download the file
    Element.click();
    Thread.sleep(2000);

    // Check if file exists
    System.out.println(jse.executeScript("browserstack_executor: {\"action\": \"fileExists\", \"arguments\": {\"fileName\": \"BrowserStack - List of devices to test on.csv\"}}"));

       driver.quit();
  }
}